The present invention relates to a method of effectively concentrating a plutonium nitrate solution which is produced in reprocessing spent nuclear fuel or in a wet recovery process in nuclear fuel production.
A plutonium nitrate solution has heretofore been concentrated by thermal distillation with the use of an evaporator, which, however, suffers disadvantages such that:
1) heating at a high temperature causes corrosion of the evaporator,
2) the corrosion of the evaporator allows the materials of construction for the evaporator to dissolve in the plutonium nitrate solution as impurities,
3) since nitric acid in the plutonium nitrate solution is also concentrated by heating, the corrosion of the evaporator is further accelerated, and a step of adjusting acid concentration after the concentration step is required, and
4) heating at a high temperature creates a possible hazard of fire or explosion.